Many prior art chemical dispensers for commercial dishwashers use conductivity probes to determine when detergent should be added to the "bath" of water used by the dishwasher. While this is desirable, such chemical dispensers are both expensive and require sophisticated personnel for proper installation, and thus such chemical dispensers are economically worthwhile only for dishwashers that process very high quantities of dishes, and thus use large quantities of chemicals. U.S. Pat. No. 4,756,321 is an example of a dishwasher chemical dispenser that uses a conductivity probe. Another prior art chemical dispenser for commercial dishwasher is shown in U.S. Pat. No. 4,509,543 (Livingston et al.). For the purposes of providing background information regarding commercial dishwashers and controllers, U.S. Pat. Nos. 4,509,543 and 4,756,321 are hereby incorporated by reference.
The prior art also includes various "probeless" chemical dispensers for commercial dishwashers. This class of chemical dispensers typically is used with smaller volume dishwashers. The controllers for most such chemical dispensers are hardwired circuits designed to implement a single dispensing protocol.
It is typical of most dishwasher liquid chemical dispenser controllers that the controller receives electrical power indirectly from the dishwasher only when the dishwasher is running. More particularly, in the typical controller, the part of the controller for running each pump is powered on only when a corresponding signal from the dishwasher's sequencer is active. For instance, in some controllers the control circuitry for running the rinse agent pump would receive power only when the rinse (i.e., fresh) water solenoid valve in the dishwasher was open, and the control circuitry for running the detergent pump would receive power only when the water tank pump (for recycling water from the dishwasher's water tank through the sprayer arms) was on.
While this may not have been viewed as a problem in the past, the above mode of powering the controller is expensive because the controller requires multiple signals from the dishwasher's sequencer, and for each such signal from the dishwasher's sequencer the controller would require a separate transformer.
It is an object of the present invention to provide a chemical dispenser controller that can be used with both door type and conveyor type dishwashers, and that can be trained or programmed at the site of the dishwasher to perform the chemical dispensing protocol required by that dishwasher. It is a related object of the present invention to provide a single probeless liquid chemical dispenser controller than can replace many, if not all, of the existing multiple models of probeless controllers.